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The early history of the Airplaneo 




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EARLY Ht/TORY 

• Or fne • • 

AIRPLANE 




OAYTON-WRIGHT AIRPLANE Oa 

OAYTON*OHIO 





LIBRARY 

UNIVERSITY OF CALIFORNIA 
DAVIS 



Digitized by the Internet Archive 

in 2007 with funding from 

IVIicrosoft Corporation 



http://www.archive.org/details/earlyhistoryofaiOOwrigrich 



The IDright Brothers' Aeroplane 



By OrvilU and Wilbur Wright 



^ m I >HOUGH the subject of aerial 
Y l"^ navigation is generally consid- 
\^j J ered new, it has occupied the 
^^ minds of men more or less 
from the earliest ages. Our personal in- 
terest in it dates from our childhood 
days. Late in the autumn of 1878 our 
father came into the house one evening 
with some object partly concealed in his 
hands, and before we could see what it 
was, he tossed it into the air. Instead of 
falling to the floor, as we expected, it flew 
across the room, till it struck the ceiling, 
where it fluttered awhile, and finally 
sank to the floor. It was a little toy, 
known to scientists as a "helicoptere," 
but which we, with sublime disregard for 
science, at once dubbed a "bat." It was 
a light frame of cork and bamboo, cov- 
ered with paper, which formed two 
screws, driven in opposite directions by 
rubber bands under torsion. A toy so 
delicate lasted only a short time in the 
hands of small boys, but its memoiy was 
abiding. 

Several years later we began building 
these helicop teres for ourselves, making 
each one larger than that preceding. But, 
to our astonishment, we found that the 
larger the "bat" the less it flew. Wejlid 
noMaixDw^tlial^^^nachir^^ only 

twicejh e Imear dimensions of another 
wouldrgguire^ightjt imes the power. We 
finally became discouragedTandreturned 
to kite-flying, a sport to which we had de- 
voted so much attention that we were 
regarded as experts. But as we became 
older we had to give up this fascinating 
sport as unbecoming to boys of our ages. 

It was not till the news of the sad death 
of Lilienthal reached America in the 



summer of 1896 that we again gave more 
than passing attention to the subject of 
flying. We then studied with great in- 
terest Chanute's "Progress in Flying Ma- 
chines," Langley's "Experiments in 
Aerodynamics," the "Aeronautical An- 
nuals" of 1905, 1906, and 1907, and sev- 
eral pamphlets published by the Smith- 
sonian Institution, especially articles by 
Lilienthal and extracts from Mouillard's 
"Empire of the Air." The larger works 
gave us a good understanding of the na- 
ture of the flying problem, and the diffi- 
culties in past attempts to solve it, while 
Mouillard and Lilienthal, the great mis- 
sionaries of the flying cause, infected us 
with their own unquenchable enthusi- 
asm, and transformed idle curiosity into 
the active zeal of workers. 

In the field of aviation there were two 
schools. The first, represented by such 
men as Professor Langley and Sir Hiram 
Maxim, gave chief attention to power 
flight; the second, represented by Lilien- 
thal, Mouillard, and Chanute, to soaring 
flight. Our sympathies were with the 
latter school, partly from impatience at 
the wasteful extravagance of mounting 
delicate and costly machinery on wings 
which no one knew how to manage, and 
partly, no doubt, from the extraordinary 
charm and enthusiasm with which the 
apostles of soaring flight set forth the 
beauties of sailing through the air on 
fixed wdngs, deriving the motive power 
from the wind itself. 

The balancing of a flyer may seem, at 
first thought, to be a very simple matter, 
yet almost ever>' experimenter had found 
in this one point which he could not sat- 
isfactorily master. Many diflerent meth- 



LIBRARV 

UNIVERSITY OF CALIFORNIA 

DAVIS 



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EARLY 



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AIRPLANE 



ods were tried. Some experimenters 
placed the center of gravity far below 
the wings, in the belief that the weight 
would naturally seek to remain at the 
lowest point. It is true, that, like the 
pendulum, it tended to seek the lowest 
point; but also, like the pendulum, it 
tended to oscillate in a manner destruc- 
tive of all stability. A more satisfactory 
system, especially for lateral balance, 
was that of arranging the wings in the 
shape of a broad V, to form a dihedral 
angle, with the center low and the wing- 
tips elevated. In theory this was an au- 
tomatic system, but in practice it had two 
serious defects: first, it tended to keep 
the machine oscillating; and second, its 
usefulness was restricted to calm air. 

In a slightly modified form the same 
system was applied to the fore-and-aft 
balance. The main aeroplane was set at 
a positive angle, and a horizontal tail at 
a negative angle, while the center of 
gravity was placed far forward. As in 
the case of lateral control, there was a 
tendency to constant undulation, and the 
very forces which caused a restoration 
of balance in calms caused a disturbance 
of the balance in winds. Notwithstand- 
ing the known limitations of this prin- 
ciple, it had been embodied in almost 
every prominent flying machine which 
had been built. 

After considering the practical effect 
of the dihedral principle, we reached the 
conclusion that a flyer founded upon it 
might be of interest from a scientific 
point of view, but could be of no value 
in a practical way. We therefore re- 
solved to try a fundamentally different 
principle. We would arrange the ma- 
chine so that it would not tend to right 
itself. We would make it as inert as 
possible to the effects of change of direc- 
tion or speed, and thus reduce the effects 
of wind-gusts to a minimum. We would 
do this in the fore-and-aft stability by 



giving the aeroplanes a peculiar shape; 
and in the lateral balance by arching the 
surfaces from tip to tip, just the reverse 
of what our predecessors had done. Then 
by some suitable contrivance, actuated 
by the operator, forces should be brought 
into play to regulate the balance. 

Lilienthal and Chanute had guided and 
balanced their machines, by shifting the 
weight of the operator's body. But this 
method seemed to us incapable of ex- 
pansion to meet large conditions, be- 
cause the weight to be moved and the 
distance of possible motion were limited, 
while the disturbing forces steadily in- 
creased, both with wing area and with 
wind velocity. In order to meet the 
needs of large machines, we wished to 
employ some system whereby the oper- 
ator could vary at will the inclination of 
different parts of the wings, and thus ob- 
tain from the wind forces to restore the 
balance which the wind itself had dis- 
turbed. This could easily be done by 
Using wings capable of being warped, and 
by supplementary adjustable surfaces in 
the shape of rudders. As the forces ob- 
tainable for control would necessarily 
increase in the same ratio as the disturb- 
ing forces, the method seemed capable of 
expansion to an almost unlimited extent. 
A happy device was discovered whereby 
the apparently rigid system of super- 
posed surfaces, invented by Wenham, 
and improved by Stringfellow and 
Chanute, could be warped in a most un- 
expected way, so that the aeroplanes 
could be presented on the right and left 
sides at different angles to the wind. 
This, with an adjustable, horizontal front 
rudder, formed the main feature of our 
first glider. 

The period from 1885 to 1900 was one 
of unexampled activity in aeronautics, 
and for a time there was high hope that 
the age of flying was at hand. But Max- 
im, after spending $100,000, abandoned 



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AIRPLANE 



the work; the Ader machine, built at the 
expense of the French Government, was 
a failure; Lilienthal and Pitcher were 
killed in experiments; and Chanute and 
many others, from one cause or another, 
had relaxed their efforts, though it sub- 
sequently became known that Professor 
Langley was still secretly at work on a 
machine for the United States Govern- 
ment. The public, discouraged by the 
failures and tragedies just witnessed, 
considered flight bej'ond the reach of 
man, and classed its adherents with the 
inventors of perpetual motion. 

We began our active experiments at 
the close of this period, in October, 1900, 
at Kitty Hawk, North Carolina. Our ma- 
chine was designed to be flown as a kite, 
with a man on board, in winds from 15 
to 20 miles an hour. But, upon trial, it 
was found that much stronger winds 
were required to lift it. Suitable winds 
not being plentiful, we found it neces- 
sary, in order to test the new balancing 
system, to fly the machine as a kite with- 
out a man on board, operating the levers 
through cords from the ground. This 
did not give the practice anticipated, but 
it inspired confidence in the new system 
of balance. 

In the summer of 1901 we became per- 
sonally acquainted with Mr. Chanute. 
When he learned that we were interested 
in flying as a sport, and not with any ex- 
pectation of recovering the money we 
were expending on it, he gave us much 
encouragement. At our invitation, he 
spent several weeks with us at our camp 
at Kill Devil Hill, four miles south of 
Kitty Hawk, during our experiments of 
that and the two succeeding years. He 
also witnessed one flight of the power 
machine near Dayton, Ohio, in October, 
1904. 

The machine of 1901 was built with 
the shape of surface used by Lilienthal, 
curved from front to rear like the seg- 



ment of a parabola, with a curvature 
1/12 the depth of its cord; but to make 
doubly sure that it would have sufficient 
lifting capacity when flown as a kite in 
15 or 20-mile winds, we increased the 
area from 165 square feet, used in 1900, 
to 308 square feet — a size much larger 
than Lilienthal, Pitcher, or Chanute had 
deemed safe. Upon trial, however, the 
lifting capacity again fell very far short 
of calculation, so that the idea of secur- 
ing practice while flying as a kite had to 
be abandoned. Mr. Chanute, who wit- 
nessed the experiments, told us that the 
trouble was not due to poor construction 
of the machine. We saw only one other 
explanation — that the tables of air-pres- 
sures in general use were incorrect. 

We then turned to gliding — coasting 
downhill on the air — ^as the only method 
of getting the desired practice in balanc- 
ing a machine. After a few minutes' 
practice we were able to make glides of 
over 300 feet, and in a few days were 
safely operating in 27-mile winds. In 
these experiments we met with several 
unexpected phenomena. We found that, 
contrary to the teachings of the books, 
the center of pressure on a curved sur- 
face traveled backward when the surface 
was inclined, at small angles, more and 
more edgewise to the wind. We also dis- 
covered that in free flight, when the wing 
on one side of the machine was presented 
to the wind at a greater angle than the 
one on the other side, the wing with the 
greater angle descended, and the machine 
turned in a direction just the reverse of 




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AIRPLANE 



what we were led to expect when flying 
the machine as a kite. The larger angle 
gave more resistance to forward motion, 
and reduced the speed of the wing on 
that side. The decrease in speed more 
than counterbalanced the eflect of the 
larger angle. The addition of a fixed 
vertical vane in the rear increased the 
trouble, and made the machine absolute- 
ly dangerous. It was some time before 
a remedy was discovered. This consisted 
of movable rudders working in conjunc- 
tion with the twisting of the wings. The 
details of this arrangement are given in 
specifications published several years 
ago. 

The experiments of 1901 were far 
from encouraging. Although M r . 
Chanute assured us that, both in control 
and in weight carried per horse-power, 
the results obtained were better than 
those of any of our predecessors, yet we 
saw that the calculations upon which all 
flying machines had been based were un- 
reliable, and that all were simply groping 
in the dark. Having set out with abso- 
lute faith in the existing scientific data, 
we were driven to doubt one thing after 
another, till finally, after two years of 
experiment, we cast it all aside, and de- 
cided to rely entirely upon our own in- 
vestigations. Truth and error were 
everywhere so intimately mixed as to be 
undistinguishable. Nevertheless, the 
time expended in preliminary study of 
books was not misspent, for they gave us 
J a good general understanding of the sub- 
ject, and enabled us at the outset to avoid 
effort in many directions in which re- 
sults would have been hopeless. 

The standard measurements of wind- 
pressures is the force produced by a cur- 
rent of air of one mile per hour velocity 
striking square against a plane of one 
square foot area. The practical difficul- 
ties of obtaining an exact measurement 
of this force have been great. The meas- 



/ 



urements by different recognized author- / 
ities vary 50 i^er cent. When this simp- 
lest of measurements presents so great 
difficulties, what shall be said of the 
troubles encountered by those who at- 
tempt to find the pressure at each angle 
as the plane is inclined more and more 
edgewise to the wind? In the eighteenth 
centui*y the French Academy prepared 
tables giving such information, and at a 
later date the Aeronautical Society of 
Great Britain made similar experiments. 
Manj' persons likewise published meas- 
urements and formulas; but the results 
were so discordant that Professor Lang- 
ley undertook a new series of measure- 
ments, the results of which form the 
basis of his celebrated work, "Experi- 
ments in Aerodynamics." Yet a critical 
examination of the data upon which he 
based his conclusions as to the pressures 
at small angles shows results so various 
as to make many of his conclusions little 
better than guesswork. 

To work intelligently, one needs to 
know the effects of a multitude of varia- 
tions that could be incorporated in the 
surfaces of flying machines. The pres- 
sures on squares are different from 
those on rectangles, circles, triangles, or 
ellipses; arched surfaces differ from 
planes, and vary among themselves ac- 
cording to the depth of cur\'ature; true 
arcs differ from parabolas, and the latter 
differ among themselves; thick surfaces 
differ from thin, and surfaces thicker in 
one place than another vary in pressure 
when the positions of maximum thick- 
ness are difterent; some surfaces are 
most efficient at one angle, others at other 
angles. The shape of the edge also makes 
a difference, so that thousands of com- 
binations are possible in so simple a 
thing as a wing. 

We had taken up aeronautics merely 
as a sport. We reluctantly entered upon 
the scientific side of it. But we soon 



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AIRPLANE 



found the work so fascinating that we 
were drawn into it deeper and deeper. 
Two testing machines were built, which 
we believed would avoid the errors to 
which the measurements of others had 
been subject. After making preliminary 
measurements on a great number of dif- 
ferent-shaped surfaces, to secure a gen- 
eral understanding of the subject, we be- 
gan systematic measurements of stan- 
dard surfaces, so varied in design as to 
bring out the underlying causes of dif- 
ferences noted in their pressures. Meas- 
urements were tabulated on nearly 50 of 
these at all angles from zero to 45 de- 
grees at intervals of 2i/2 degrees. Meas- 
urements were also secured showing the 
effects on each other when surfaces are 
superposed, or when they follow one an- 
other. 

Some strange results were obtained. 
One surface, with a heavy roll at the 
front edge, showed the same lift for all 
angles from 7I/2 to 45 degrees. A square 
plane, contrary to the measurements of 
all our predecessors, gave a greater pres- 
sure at 30 degrees than at 45 degrees. 
This seemed so anomalous that we were 
almost ready to doubt our own measure- 
ments, when a simple test was suggested. 
A weather-vane, with two planes attached 
to the pointer at an angle of 80 degrees 
with each other, was made. According 
to our tables, such a vane would be in 
unstable equilibrium when pointing di- 
rectly into the wind; for if by chance the 
wind should happen to strike one plane 
at 39 degrees and the other at 41 degrees, 
the plane with the smaller angle would 
have the greater pressure, and the pointer 
would be turned still farther out of the 
course of the wind until the two vanes 
again secured equal pressures, which 
would be at approximately 30 and 50 de- 
grees. But the vane performed in this 
very manner. Further corroboration of 
the tables was obtained in experiments 



with the new glider at Kill Devil Hill the 
next season. 

In September and October, 1902, near- 
ly 1,000 gliding flights were made, sev- 
eral of whicli covered distances of over 
600 feet. Some, made against a wind of 
36 miles an hour, gave proof of the ef-^ 
fectiveness of the devices for control. 
With this machine, in the autumn of 
1903, we made a number of flights in 
which we remained in the air for over a 
minute, often soaring for a considerable 
time in one spot, without any descent at 
all. Little wonder that our unscientific 
assistant should think the only thing 
needed to keep it indefinitely in the air 
would be a coat of feathers to make it 
light! 

With accurate data for making calcu- 
lations, and a system of balance effective 
in winds as well as in calms, we were 
now in a position, we thought, to build a 
successful power-flyer. The first designs 
provided for a total weight of 600 lbs., in- 
cluding the operator and an eight horse- 
power motor. But, upon completion, the 
motor gave more power than had been 
estimated, and this allowed 150 lbs. to be 
added for strengthening the wings and 
other parts. , 

Our tables made the designing of the 
wings an easy matter, and as screw- 
propellers are simply wings traveling in 
a spiral course, we anticipated no trouble 
from this source. W^e had thought of 
getting the theory of the screw-propeller 
from the marine engineers, and then, by 
applying our tables of air-pressures to 
their formulas, of designing air-propel-y 
lers suitable for our purpose. But so far 
as we could learn, the marine engineers 
possessed only empirical formulas, and 
the exact action of the screw-propeller, 
after a century of use, was still very ob- 
scure. As we were not in a position to 
undertake a long series of practical ex- 
periments to discover a propeller suitable 



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AIRPLANE 



for our machine, it seemed necessary to 
obtain such a thorough understanding 
of the theory of its reactions as would 
enable us to design them from calcula- 
tions alone. What at first seemed a prob- 
lem became more complex the longer we 
studied it. With the machine moving 
forward, the air flying backward, the 
propellers turning sidewise, and nothing 
standing still, it seemed impossible to find 
a starting-point from which to trace the 
various simultaneous reactions. Con- 
templation of it was confusing. After 
long arguments we often found our- 
selves in the ludicrous position of each 
having been converted to the other's side, 
with no more agreement than when the 
discussion began. 

It was not till several months had 
passed, and every phase of the problem 
had been thrashed over and over, that 
the various reactions began to untangle 
themselves. When once a clear under- 
standing had been obtained there was no 
difficulty in designing suitable propellers, 
with proper diameter, pitch, and area of 
blade, to meet the requirements of the 
flyer. High eflQciency in a screw-propel- 
ler is not dependent upon any particular 
or peculiar shape; and there is no such 
thing as a "best" screw. A propeller giv- 
ing a high dynamic efficiency when used 
upon one machine may be almost worth- 




less when used upon another. The 
propeller should in every case be 
designed to meet the particular condi- 
tions of the machine to which it is to be 
applied. Our first propellers, built en- . 
tirely from calculation, gave in useful ^ 
work 66 per cent, of the power expended. 
This was about one-third more than had 
been secured by Maxim or Langley. 

The first flights with the power ma- 
chine were made on December 17, 1903. 
Only five persons besides ourselves were 
present. These were Messrs. John T. 
Daniels, W. S. Dough, and A. D. Ether- 
idge, of the Kill Devil Life-Saving Sta- 
tion; Mr. W. C. Brinkley, of Manteo; and 
Mr. John Ward, of Naghead. Although 
a general invitation had been extended 
to the people living within five or six 
miles, not many were willing to face the 
rigors of a cold December wind in order 
to see, as they no doubt thought, another 
flying machine not fly. The first flight 
lasted only 12 seconds, a flight very mod- 
est compared with that of birds, but it 
was, nevertheless, the first in the history 
of the world in which a machine carry- 
ing a man had raised itself by its own 
power into the air in free flight, had 
saileed forward on a level course without 
reduction of speed, and had finally land- 
ed without being wrecked. The second 
and third flights were a little longer, and 
the fourth lasted 59 seconds, covering a 
distance of 852 feet over the ground 
against a 20-mile wind. 

After the last flight the machine was 
carried back to camp and set down in 
what was thought to be a safe place. But 
a few minutes later, while we were en- 
gaged in conversation about the flights, a 
sudden gust of wind struck the machine, 
and started to turn it over. All made a 
rush to stop it, but we were too late. 
Mr. Daniels, a giant in stature and 
strength, was lifted off his feet, and fall- 
ing inside, between the surfaces, was 



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shaken about like a rattle in a box as the 
machine rolled over and over. He finally 
fell out upon the sand with nothing worse 
than painful bruises, but the damage to 
the machine caused a discontinuance of 
experiments. 

In the spring of 1904, through the 
kindness of Mr. Torrence Huffman, of 
Daj'ton, Ohio, we were permitted to erect 
a shed, and to continue experiments, on 
what is known as the Huffman Prairie, 
at Simms Station, eight miles east of Day- 
ton. The new machine was heavier and 
stronger, but similar to the one flown at 
Kill Devil Hill. When it was ready for 
its first trial every newspaper in Dayton 
was notified, and about a dozen represen- 
tatives of the Press were present. Our 
only request was that no pictures be 
taken, and that the reports be unsensa- 
tional, so as not to attract crowds to our 
experiment grounds. There were prob- 
ably 50 persons altogether on the ground. 
When preparations had been completed 
a wind of only three or four miles was 
blowing — insufficient for starting on so 
short a track — but since many had come 
a long way to see the machine in action, 
an attempt was made. To add to the 
other difficulty, the engine refused to 
work properly. The machine, after run- 
ning the length of the track, slid off the 
end without rising into the air at all. 
Several of the newspaper men returned 
the next day, but were again disappoint- 
ed. The engine performed badly, and 
after a glide of only 60 feet, the machine 
came to the ground. Further trial was 
postponed till the motor could be put in 
better running condition. The reporters 
had now, no doubt, lost confidence in the 
machine, though their reports, in kind- 
ness, concealed it. Later, when they 
heard that we were making flights of sev- 
eral minutes' duration, knowing that 
longer flights had been made with air- 



ships, and not knowing any essential dif- 
ference between airships and flying ma- 
chines, they were but little interested. 

We had not been flying long in 1904 
before we found that the problem of 
equilibrium had not as yet been entirely 
solved. Sometimes, in making a circle, 
the machine would turn over sidewise 
despite anything the operator could do, 
although, under the same conditions in 
ordinary straight flight, it could have 
been righted in an instant. In one flight, 
in 1905, while circling around a honey 
locust tree at a height of about 50 feet, 
the machine suddenly began to turn up 
on one wing, and took a course toward 
the tree. The operator, not relishing the 
idea of landing in a thorn-tree, attempted 
to reach the ground. The left wing, 
however, struck the tree at a height of 10 
or 12 feet from the ground and carried 
away several branches; but the flight, 
which had already covered a distance of 
six miles, was continued to the starting- 
point. 

The causes of these troubles — too tech- 
nical for explanation here — ^were not en- 
tirely overcome till the end of Septem- 
ber, 1905. The flights then rapidly in- 
creased in length, till experiments were 
discontinued after October 5, on account 
of the number of people attracted to the 
field. Although made on a ground open 
on every side, and bordered on two sides 
by much-traveled thoroughfares, with 
electric cars passing every hour, and seen 
by aU the people living in the neighbor- 
hood for miles around, and by several 
hundred others, yet these flights have 
been made by some newspapers the sub- 
ject of a great "mystery." 

A practical flyer having been finally 
realized, we spent the years 1906 and 
1907 in constructing new machines and 
in business negotiations. It was not till 
May of this year that experiments (dis- 
continued in October, 1905) were re- 



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AIRPLANE 



sumed at Kill Devil Hill, North Carolina. 
The recent flights were made to test the 
ability of our machine to meet the re- 
quirements of a contract with the United 
States Government to furnish a flyer 
capable of carrying two men and sutli- 
cient fuel supplies for a flight of 125 
miles, with a speed of 40 miles an hour. 
The machine used in these tests was the 
same one with which the flights were 
made at Simms Station in 1905, though 
several changes had been made to meet 
present requirements. The operator as- 
sumed a sitting position, instead of lying 
prone, as in 1905, and a seat was added 
for a passenger. A larger motor was in- 
stalled, and radiators and gasoline reser- 
voirs of larger capacity replaced those 
previously used. No attempt was made 
to make high or long flights. 

In order to show the general reader the 
way in which the machine operates, let 
us fancy ourselves ready for the start. 
The machine is placed upon a single-rail 
track facing the wind, and is securely 
fastened with a cable. The engine is put 
in motion, and the propellers in the rear 
whir. You take j^our seat at the center 
of the machine beside the operator. He 
slips the cable, and you shoot forward. 
An assistant who has been holding the 
machine in balance on the rail starts for- 
ward with you, but before you have gone 
50 feet the speed is too great for him, and 
he lets go. Before reaching the end of 
the track the operator moves the front 
rudder, and the machine lifts from the 
rail like a kite supported by the pressure 
of the air underneath it. The ground 
under you is at first a perfect blur, but as 
you rise the objects become clearer. At 
a height of 100 feet you feel hardly any 
motion at all, except for the wind which 
strikes your face. If you did not take 
the precaution to fasten your hat before 



starting, you have probably lost it by 
this time. The operator moves a lever: 
the right wing rises, and the machine 
swings about to the left. You make a 
very short turn, yet you do not feel the 
sensation of being thrown from your 
seat, so often experienced in automo- 
bile and railway travel. You find your- 
self facing toward the point from which 
you started. The objects on the ground 
now seem to be moving at much higher 
speed, though you perceive no change in 
the pressure of the wind on your face. 
You know then that you are traveling 
with the wind. When you near the start- 
ing-point the operator stops the motor 
while still high in the air. The machine 
coasts down at an oblique angle to the 
ground, and after sliding 50 or 100 feet, 
comes to rest. Although the machine 
often lands when traveling at a speed of 
a mile a minute, you feel no shock what- 
ever, and cannot, in fact, tell the exact 
moment at which it first touched the 
ground. The motor close beside you 
kept up an almost deafening roar during 
the whole flight, yet in your excitement 
you did not notice it till it stopped! 

Our experiments have been conducted 
entirelj' at our own expense. In the be- 
ginning we had no thought of recovering 
what we were expending, which was not 
great, and was limited to what we could 
afford in recreation. Later, when a suc- 
cessful flight had been made with a mo- 
tor, we gave up the business in which we 
were engaged, to devote our entire time 
and capital to the development of a ma- 
chine for practical uses. As soon as our 
condition is such that constant attention 
to business is not required, we expect to 
prepare for publication the results of our 
laboratory experiments, which alone 
made an early solution of the flying 
problem possible. 



liou? IPe Made the First Flight 

By OrvilU Wright 




.HE flights of the 1902 glider had 
demonstrated the efficiency of 
our system o f maintaining 
equihbrium, and also the accu- 
racy of the laboratory work upon which 
the design of the glider was based. We 
then felt that we were prepared to calcu- 
late in advance the performance of ma- 
chines with a degree of accuracy that had 
never been possible with the data and 
tables possessed by our predecessors. 
Before leaving camp in 1902 we were al- 
ready at work on the general design of a 
new machine which we proposed to 
propel with a motor. 

Immediately upon our return to Day- 
ton, we wrote to a number of automobile 
and motor builders, stating the purpose 
for which we desired a motor, and ask- 
ing whether they could furnish one that 
would develop eight brake-horsepower, 
with a weight complete not exceeding 200 
pounds. Most of the companies an- 
swered that they were too busy with their 
regular business to undertake the build- 
ing of such a motor for us; but one com- 
pany replied that they had motors rated 
at 8 horse-power, according to the 
French system of ratings, which weighed 
only 135 pounds, and that if we thought 
this motor would develop enough power 
for our purpose they would be glad to 
sell us one. After an examination of the 
particulars of this motor, from which 
we learned that it had but a single cylin- 
der of 4-inch bore and 5-inch stroke, we 
were afraid it was much over-rated. 
Unless the motor would develop a full 8 
brake-horsepower, it would be useless 
for our purpose. 

Finally we decided to undertake the 
building of the motor ourselves. We es- 



timated that we could make one of four 
cylinders with 4-inch bore and 4-inch 
stroke, weighing not over two hundred 
pounds, including all accessories. Our 
only experience up to that time in the 
building of gasoline motors had been in 
the construction of an air-cooled motor, 
5-inch bore and 7-incli stroke, which was 
used to run the machinery of our small 
workshop. To be certain that four cylin- 
ders of the size we had adopted (4" x 4") 
would develop the necessary 8 horse- 
power, we first fitted them in a tempor- 
ary frame of simple and cheap construc- 
tion. In just six weeks from the time the 
design was started, we had the motor on 
the block testing its power. The ability 
to do this so quickly was largely due to 
the enthusiastic and elTicient services of 
Mr. C. E. Taylor, who did all the machine 
work in our shop for the first as well as 
the succeeding experimental machines. 
There was no provision for lubricating 
either cylinders or bearings while this 
motor was running. For that reason it 
was not possible to run it more than a 
minute or two at a time. In these short 
tests the motor developed about nine 
horse-power. We were then satisfied 
that, with proper lubrication and better 
adjustments, a little more power could 




THE 



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AIRPLANE 



be expected. The completion of the mo- 
tor according to drawing was, therefore, 
proceeded with at once. 

While Mr. Taylor was engaged with 
this work, Wilbur and I were busy in 
completing the design of the machine 
itself. The preliminary tests of the mo- 
tor having convinced us that more than 
8 horse-power would be secured, we felt 
free to add enough weight to build a 
more substantial machine than we had 

originally contemplated. 

****** 

For two reasons we decided to use two 
propellers. In the first place we could, 
by the use of two propellers, secure a re- 
action against a greater quantity of air, 
and at the same time use a larger pitch 
angle than was possible with one propel- 
ler; and in the second place by having the 
propellers turn in opposite direction, the 
gyroscopic action of one would neutral- 
ize that of the other. The method we 
adopted of driving the propellers in op- 
posite directions by means of chains is 
now too well known to need description 
here. We decided to place the motor to 
one side of the man, so that in case of a 
plunge headfirst, the motor could not fall 
upon him. In our gliding experiments 
w^e had had a numbei- of experiences in 
which we had landed upon one wing, but 
the crushing of the wing had absorbed 
the shock, so that we were not uneasy 
about the motor in case of a landing of 
that kind. To provide against the ma- 
chine rolling over forward in landing, we 
designed skids like sled runners, extend- 
ing out in front of the main surfaces. 
Otherwise the general construction and 
operation of the machine was to be simi- 
lar to that of the 1902 glider. 

When the motor was completed and 
tested, we found that it would develop 16 
horse-power for a few seconds, but that 
the power rapidlj^ dropped till, at the end 
of a minute, it was only 12 horse-power. 



Ignorant of what a motor of this size 
ought to develop, we were greatly pleased 
with its performance. More experience 
showed us that we did not get one-half 
of the power we should have had. 

With 12 horse-power at our command, 
we considered that we could pennit the 
weight of the machine with operator to 
rise to 750 or 800 pounds, and still have 
as much surplus power as we had orig- 
inally allowed for in the first estimate of 
550 pounds. 

Before leaving for our camp at Kitty 
Hawk we tested the chain drive for tlie 
propellers in our shop at Dayton, and 
found it satisfactory. We found, how- 
ever, that our first propeller shafts, 
which were constructed of heavy gauge 
steel tubing, were not strong enough to 
stand the shocks received from a gaso- 
line motor with light fly wheel, although 
they would have been able to ti'ansmit 
three or four times the power uniformly 
applied. We therefore built a new set of 
shafts of heavier tubing, which we tested 
and thought to be abundantly strong. 

We left Dayton, September 23, and ar- 
rived at our camp at Kill Devil Hill on 
Friday, the 25th. We found there pro- 
visions and tools, which had been ship- 
ped by freight several weeks in advance. 
The building, erected in 1901 and en- 
larged in 1902, was found to have been 
blown by a stonn from its foundation 
posts a few months previously. While 
we were awaiting the arrival of the ship- 
ment of machinery and parts from Day- 
ton, we were busy putting the old build- 
ing in repair, and erecting a new build- 
ing to serve as a workshop for assemb- 
ling and housing the new machine. 

Just as the building was being com- 
pleted, the parts and material for the ma- 
chines arrived simultaneously with one 
of the worst storms that had visited Kitty 
Hawk in years. The storm came on sud- 
denly, blowing 30 to 40 miles an hour. 



w 



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AIRPLANE 



It increased during the night, and the 
next day was blowing over 75 miles an 
hour. In order to save the tar-paper 
roof, we decided it would be necessary 
to get out in this wind and nail down 
more securely certain parts that were 
especially exposed. When I ascended 
the ladder and reached the edge of the 
roof, the wind caught under my large 
coat, blew it up around my head and 
bound my arms till I was perfectly help- 
less. Wilbur came to mj' assistance and 
held down my coat while I tried to drive 
the nails. But the wind was so strong I 
could not guide the hammer and succeed- 
ed in striking my fingers as often as the 
nails. 

The next three weeks were spent in 
setting the motor-machine together. On 
days with more favorable winds we 
gained additional experience in handling 
a flyer bj^ gliding with the 1902 machine, 
which we had found in pretty fair condi- 
tion in the old building, where we had 
left it the year before. 

Mr. Chanute and Dr. Spratt, who had 
been guests in our camp in 1901 and 
1902, spent some time with us, but neith- 
er one was able to remain to see the test 
of the motor-machine, on account of the 
delays caused by trouble which devel- 
oped in the propeller shafts. 

While Mr. Chanute was with us, a good 
deal of time was spent in discussion of 
the mathematical calculations upon 
which we had based our machine. He 
informed us that, in designing machin- 
ery, about 20 per cent, was usually al- 
lowed for the loss in the transmission of 
powej*. As we had allowed only 5 per 
cent., a figure we had arrived at by some 
crude measurements of the friction of 
one of tlie cliains when carrying only a 
very light load, we were much alanned. 
More than the whole surplus in power al- 
lowed in our calculations would, accord- 
ing to Mr. Ghanute's estimate, be con- 



sumed in friction in the driving chains. 
After Mr. Ghanute's departure, we sus- 
pended one of the drive chains over a 
sprocket, hanging bags of sand on either 
side of the sprocket of a weight approx- 
imately equal to the pull that would be 
exerted on the chains when driving the 
propellers. By measuring the extra 
amount of weight needed on one side to 
lift the weight on the other, we calcu- 
lated the loss in transmission. This indi- 
cated that the loss of power from this 
source would be only 5 per cent., as we 
originally estimated. But while we 
could see no serious error in this method 
of determining the loss, we were very 
uneasy until we had a chance to run the 
propellers with the motor to see whether 
we could get the estimated number of 
turns. 

The first run of the motor on the ma- 
chine developed a flaw in one of the 
propeller shafts which had not been dis- 
covered in the test at Dayton. The shafts 
were sent at once to Daj'ton for repair, 
and were not received again until No- 
vember 20, having been gone two weeks. 
We immediately put them in the machine 
and made another test. A new trouble 
developed. The sprockets which were 
screwed on the shafts, and locked with 
nuts of opposite thread, persisted in com- 
ing loose. After many futile attempts to 
get them fast, we had to give it up for 
that day, and went to bed much discour- 
aged. However, after a night's rest, we 
got up the next morning in better spirits 
and resolved to try again. 

While in the bicycle business we had 
become well acquainted with the use of 
hard tire cement for fastening tires on 
the rims. We had once used it success- 
fully in repairing a stop watch after sev- 
eral watchsmiths had told us it could not 
be repaired. If tire cement was good for 
fastening the hands on a stop watch, why- 
should it not be good for fastening the 



u 



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AIRPLANE 



sprockets on the propeller shaft of a fly- 
ing machine? We decided to try it. We 
heated the shafts and sprockets, melted 
cement into the threads, and screwed 
them together again. This trouble was 
over. The sprockets stayed fast. 

Just as the machine was ready for test 
bad weather set in. It had been disagree- 
ably cold for several weeks, so cold that 
we could scarcely work on the machine 
for some days. But now we began to 
have rain and snow, and a wind of 25 to 
30 miles blew for several days from the 
north. While we were being delayed by 
the weather we arranged a mechanism to 
measure automatically the duration of a 
flight from the time the machine started 
to move forward to the time it stopped, 
the distance traveled through the air in 
that time, and the number of revolutions 
made by the motor and propeller. A 
stop watch took the time; an anemo- 
meter measured the air traveled 
through; and a counter took the number 
of revolutions made by the propellers. 
The watch anemometer and revolution 
counter were all automatically started 
and stopped simultaneously. From data 
thus obtained we expected to prove or 
disprove the accuracy of our propeller 
calculations. 

On November 28, while giving the mo- 
tor a run indoors, we thought we again 
saw something wrong with one of the 
propeller shafts. On stopping the motor 
we discovered that one of the tubular 
shafts had cracked! 

Immediate preparation was made for 
returning to Dayton to build another set 
of shafts. We decided to abandon the 




use of tubes, as they did not afford 
enough spring to take up the shocks of 
premature or missed explosions of the 
motor. Solid tool-steel shafts of smaller 
diameter tJian the tubes previouslj' used 
were decided upon. These would allow 
a certain amount of spring. The tubular 
shafts were many times stronger than 
would have been necessary to transmit 
the power of our motor if the strains up- 
on them had been unifonn. But the 
large hollow shafts had no spring in them 
to absorb the unequal strains. 

Wilbur remained in camp while I went 
to get the new shafts. I did not get back 
to camp again till Friday, the 11th of De- 
cember. Saturday afternoon the ma- 
chine was again ready for trial, but the 
wind was so light a start could not have 
been made from level ground with the 
run of only sixty feet permitted by our 
monorail track. Nor was there enough 
time before dark to take the machine to 
one of the hills, where, by placing the 
track on a steep incline, sufficient speed 
could be secured for starting in calm air. 

Monday, December 14, was a beautiful 
day, but there was not enough wind to 
enable a start to be made from the level 
ground about camp. We therefore de- 
cided to attempt a flight from the side of 
the big Kill Devil Hill. We had arranged 
with the members of the Kill Devil Hill 
Life Saving Station, which was located a 
little over a mile from our camp, to in- 
form them when we were ready to make 
the first trial of the machine. We were 
soon joined by J. T. Daniels, Robert 
Westcott, Thomas Beachem, W. S. Dough 
and Uncle Benny O'Neal, of the station, 
who helped us get the machine to the hill, 
a quarter mile away. We laid the track 
150 feet up the side of the hill on a 9-de- 
gree slope. With the slope of the track, 
the thrust of the propellers and the ma- 
chine starting directly into the wind, we 
did not anticipate any ti'ouble in getting 



i« 



THE 



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HISTORY 



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THE 



AIRPLANE 



up flying speed on the 60-foot monorail 
track. But we did not feel certain the 
operator could keep the machine bal- 
anced on the track. 

When the machine had been fastened 
with a wire to the track, so that it could 
not start until released by the operator, 
and the motor had been run to make sure 
that it was in condition, we tossed up a 
coin to decide who should have the first 
trial. Wilbur won. I took a position at 
one of the wings, intending to help bal- 
ance the machine as it ran down the 
track. But when the restraining wire 
was slipped, the machine started off so 
quickly I could stay with it only a few 
feet. After a 35 to 40-foot run it lifted 
from the rail. But it was allowed to turn 
up too much. It climbed a few feet, 
stalled, ^nd then settled to the ground 
near the foot of the hill, 105 feet below. 
My stop watch showed that it had been 
in the air just 3l^ seconds. In landing 
the left wing touched first. The machine 
swung around, dug the skids into the 
sand and broke one of them. Several 
other parts were also broken, but the 
damage to the machine was not serious. 
While the test had shown nothing as to 
whether the power of the motor was suf- 
ficient to keep the machine up, since the 
landing was made many feet below the 
starting point, the experiment had dem- 
onstrated that the method adopted for 
launching the machine was a safe and 
practical one. On the whole, we were 
much pleased. 

Two days were consumed in making 
repairs, and the machine was not ready 
again till late in the afternoon of the 
16th. While we had it out on the track 
in front of the building, making the final 
adjustments, a stranger came along. 
After looking at the machine a few sec- 
onds he inquired what it was. When we 
told him it was a flying machine he asked 
whether we intended to fly it. We said 



we did, as soon as we had a suitable wind. 
He looked at it several minutes longer 
and then, wishing to be courteous, re- 
marked that it looked as if it would fly, 
if it had a "suitable wind." We were 
much amused, for, no doubt, he had in 
mind the recent 75-mile gale when he re- 
peated our words, "a suitable wind!" 

During the night of December 16, 
1903, a strong cold wind blew from the 
north. When we arose on the morning 
of the 17th, the puddles of water, which 
had been standing about camp since the 
recent rains, were covered with ice. The 
wind had a velocity of 10 to 12 meters per 
second (22 to 27 miles an hour). We 
thought it would die down before long, 
and so remained indoors the early part 
of the morning. But when ten o'clock 
arrived, and the wind was as brisk as 
ever, we decided that we had better get 
the machine out and attempt a flight. 
We hung out the signal for the men of 
the life saving station. We thought that 
by facing the tlyer into a strong wind, 
there ought to be no trouble in launch- 
ing it from the level ground about camp. 
We realized the difficulties of flying in 
so high a wind, but estimated that the 
added dangers in flight would be partly 
compensated for by the slower speed in 
landing. 

We laid the track on a smooth stretch 
of ground about one hundred feet north 
of the new building. The biting cold 
wind made work difficult, and we had to 
warm up frequently in our living room, 
where we had a good fire in an impro- 
vised stove made of a large carbide can. 
By the time afl was ready, J. T. Daniels, 
W. S. Dough and A. D. Etheridge, mem- 
bers of the Kill Devil Life Saving Station; 
W. C. Brinkley, of Manleo, and Johnny 
Moore, a boy from Nag's Head, had ar- 
rived. 

We had a "Richards" hand anemo- 
meter with which we measured the ve- 



» 



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THE 



AIRPLANE 



locity of the wind. , Measurements made 
just before starting the first flight showed 
velocities of 11 to 12 meters per second, 
or 24 to 27 miles per hour. Measure- 
ments made just before the last flight 
gave between 9 and 10 meters per sec- 
ond. One made just after showed a little 
over 8 meters. The records of the Gov- 
ernment Weather Bureau at Kitty Hawk 
gave the velocity of the wind between the 
hours of 10:30 and 12 o'clock, the time 
during which the four flights were made, 
as averaging 27 miles at the time of the 
first flight and 24 miles at the time of the 
last. 

***** -0 

Wilbur, having used his turn in the 
unsuccessful attempt on the 14th, the 
right to the first trial now belonged to 
me. After running the motor a few min- 
utes to heat it up, I released the wire that 
held the machine to the track, and the 
machine started forward into the wind. 
Wilbur ran at the side of the machine, 
holding the wing to balance it on the 
track. Unlike the start on the 14th, made 
in a calm, the machine, facing a 27-mile 
wind, started verj' slowly. Wilbur was 
able to stay with it till it lifted from the 
track after a forty-foot run. One of the 
life saving men snapped the camera for 
us, taking a picture just as the machine 
had reached the end of the track and had 
risen to a height of about two feet. The 
slow forward speed of the machine over 
the ground is clearly shown in the pic- 
lure by Wilbur's attitude. He stayed 
along beside the machine witliout any 
effort. 

The course of the flight up and down 
was exceedingly erratic, partly due to the 
irregularity of the air, and partly to lack 
of experience in handUng this machine. 
The control of the front rudder was difQ- 
cult on account of its being balanced too 
near the center. This gave it a tendency 
to turn itself when started; so that it 



turned too far on one side and then too 
far on the other. As a result the machine 
would rise suddenly to about ten feet, 
and then as suddenly dart for the ground. 
A sudden dart when a little over a hun- 
dred feet from the end of the track, or a 
little over 120 feet from the point at 
which it rose into the air, ended the flight. 
As the velocity of the wind was over 35 
feet per second and the speed of the ma- 
chine against this wind ten feet per sec- 
ond, the speed of the machine relative to 
the air was over 45 feet per second, and 
the length of the flight was equivalent to 
a flight of 540 feet made in calm air. 
This flight lasted only 12 seconds, but it 
was nevertheless the first in the history 
of the world in which a machine carrying 
a man had raised itself by its own power 
into the air in full flight, had sailed for- 
ward without reduction of speed, and 
had finally landed at a point as high as 
that from which it started. 

****** 

At twenty minutes after eleven Wilbur 
tarted on the second flight. The course 
of this flight was much like that of the 
first, very much up and down. The 
speed over the ground was somewhat 
faster than that of the first flight, due to 
the lesser wind. The duration of the 
flight was less than a second longer than 
the first, but the distance covered was 
about seventy-five feet greater. 

Twenty minutes later the third flight 
started. This one was steadier than the 
first one an hour before. I was proceed- 
ing along pretty well when a sudden gust 
from the right lifted the machine up 
twelve to fifteen feet and turned it up 
sidewise in an alarming manner. It be- 
gan sliding ofi" to the left. I warped the 
wings to try to recover the lateral bal- 
ance and at the same time pointed the 
machine down to reach the ground as 
quickly as possible. The lateral control 
was more effective than I had imagined 



14 



THE 



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HISTORY 



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THE 



AIRPLANE 



and before I reached the ground the right 
wing was lower than the left and struck 
first. The time of this flight was fifteen 
seconds and the distance over the ground 
a little over 200 feet. 

Wilbur started the fourth and last 
flight at just 12 o'clock. The first few 
hundred feet were up and down as be- 
fore, but by the time three hundred feet 
had been covered, the machine was un- 
der much better control. The course for 
the next four or five hundred feet had 
but little undulation. However, when 
out about eight hundred feet the machine 
began pitching again, and, in one of its 
starts downward, struck the ground. 
The distance over the ground was meas- 
ured and found to be 852 feet; the time 
of the flight 59 seconds. The frame sup- 
porting the front rudder was badly 
broken, but the main part of the ma- 
chine was not injured at all. We esti- 
mated that the machine could be put in 



condition for flight again in a day or two. 
While we were standing about discuss- 
ing this last flight, a sudden strong gust 
of wind struck the machine and began 
to turn it over. Everybody made a rush 
for it. Wilbur, who was at one end, 
seized it in front, Mr. Daniels and I, who 
were behind, tried to stop it behind, tried 
to stop it by holding to the rear uprights. 
All our efforts were vain. The machine 
rolled over and over. Daniels, who had 
retained his grip, was carried along with 
it, and was thrown about head over heels 
inside of the machine. Fortunately he 
was not seriously injured, though badly 
bruised in falling about against the mo- 
tor, chain guides, etc. The ribs in the 
surfaces of the machine were broken, the 
motor injured and the chain guides badly 
bent, so that all possibility of further 
flights with it for that year were at an 
end. 




u 



Some Aeronauticdl Experiments 



By Wilbur Wright 




HE difficulties which obstruct 
the pathway to success in fly- 
ing machine construction are 
of three general classes: (1) 
Those which relate to the construction of 
the sustaining wings. (2) Those which 
relate to the generation and application 
of the power required to drive the ma- 
chine through the air. (3) Those relat- 
ing to the balancing and steering of the 
machine after it is actually in flight. Of 
these difficulties two are already to a cer- 
tain extent solved. Men already know 
how to construct wings or aeroplanes 
which, when driven through air at suffi- 
cient speed, will not only sustain the 
weight of the wings themselves, but also 
that of the engine, and of the engineer as 
well. Men also know how to build en- 
gines and screws of sufficient lightness 
and power to drive these planes at sus- 
taining speed. As long ago as 1893 a ma- 
chine weighing 8,000 lbs. demonstrated 
its power both to lift itself from the 
ground and to maintain a speed of from 
30 to 40 miles per hour; but it came to 
grief in an accidental free flight, owing 
to the inability of the operators to bal- 
ance and steer it properly. This inability 
to balance and steer still confronts stu- 
dents of the flying problem, although 
nearly ten years have passed. When this 
one feature has been worked out the age 
of flying machines will have arrived, for 
all other difficulties are of minor im- 
portance. 

The person who merely watches the 
flight of a bird gathers the impression 
that the bird has nothing to think of but 
the flapping of its wings. As a matter of 
fact, this is a very small part of its men- 
tal labour. Even to mention all the 
things the bird must constantly keep in 



mind in order to fly securely through the 
ail' would take a very considerable trea- 
tise. If I take a piece of paper, 
and after placing it parallel with the 
ground, quickly let it fall, it will not set- 
tle steadily down as a staid, sensible piece 
of paper ought to do, but it insists on con- 
travening every recognized rule of de- 
corum, turning over and darting hither 
and thither in the most erratic manner, 
much after the style of an untrained 
horse. Yet this is the style of steed that 
men must learn to manage before flying 
can become an everyday sport. The bird 
has learned this art of equilibrium, and 
learned it so thoroughly that its skill is 
not apparent to our sight. We only learn 
to appreciate it when we try to imitate it. 
Now, there are two ways of learning how 
to ride a fractious horse: one is to get on 
him and learn by actual practice how 
each motion and trick may be best met; 
the other is to sit on a fence and watch 
the beast awhile, and then retire to the 
house and at leisure figure out the best 
way of overcoming his jumps and kicks. 
The latter system is the safest; but the 
former, on the whole, turns out the larger 
porportion of good riders. It is very 
much the same in learning to ride a flying 
machine; if you are looking for perfect 
safety you will do well to sit on a fence 
and watch the birds; but if you really 
wish to learn you must mount a machine 
and become acquainted with its tricks 
by actual trial. 

****** 

My own active interest in aeronautical 
problems dates back to the death of 
Lilienthal in 1896. The brief notice of 
his death which appeared in the tele- 
graphic news at that time aroused a pas- 
sive interest which had existed from my 



i« 



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THE 



AIRPLANE 



childhood, and led me to take down from 
the shelves of our home library a book 
on "Animal Mechanism," by Prof. 
Marey, which I had already read several 
times. From this I was led to read more 
modern works, and as my brother soon 
became equally interested with myself, 
we soon passed from the reading to the 
thinking, and finally to the working 
stage. It seemed to us that the main 
reason why the problem had remained so 
long unsolved was that no one had been 
able to obtain any adequate practice. We 
figured that Lilienthal in five years of 
time had spent only about five hours in 
actual gliding through the air. The won- 
der was not that he had done so little, but 
that he had accomplished so much. It 
would not be considered at all safe for a 
bicycle rider to attempt to ride through 
a crowded city street after only five 
hours' practice, spread out in bits of ten 
seconds each over a period of five years; 
yet Lilienthal with this brief practice was 
remarkably successful in meeting the 
fluctuations and eddies of wind gusts. 
We thought that if some method could be 
found by which it would be possible to 
practice by the hour instead of by the 
second there would be hope of advancing 
the solution of a very difficult problem. 
It seemed feasible to do this by building 
a machine which would be sustained at 
a speed of 18 miles per hour, and then 
finding a locality where winds of this ve- 
locity were common. With these condi- 
tions a rope attached to the machine to 
keep it from floating backward would 
answer very nearly the same purpose as 
a propeller driven by a motor, and it 
would be possible to practice by the hour, 
and without any serious danger, as it 
would not be necessary to rise far from 
the ground, and the machine would not 
have any forward motion at all. We 
found, according to the accepted tables of 
air pressures on curved surfaces, that a 



machine spreading 200 square feet of 
wing surface would be sufficient for our 
purpose, and that places could easily be 
found along the Atlantic coast where 
winds of 16 to 25 miles were not at aU 
uncommon. When the winds were low 
it was our plan to glide from the tops of 
sand hills, and when they were sufficient- 
ly strong to use a rope for our motor and 
fly over one spot. Our next work was to 
draw up the plan for a suitable machine. 
After much study we finally concluded 
that tails were a source of trouble rather 
than of assistance, and therefore we de- 
cided to dispense with them altogether. 
It seemed reasonable that if the body of 
the operator could be placed in a horizon- 
tal position instead of the upright, as in 
the machines of Lilienthal, Pitcher and 
Chanute, the wind resistance could be 
very materially reduced, since only one 
square foot instead of five would be ex- 
posed. As a full half-horse-power could 
be saved by this change, we arranged to 
try at least the horizontal position. Then 
the method of control used by Lilienthal, 
which consisted in shifting the body, did 
not seem quite as quick or effective as the 
case required; so, after long study, we 
contrived a system consisting of two 
large surfaces on the Chanute double- 
deck plan, and a smaller surface placed 
a short distance in front of the main sur- 
faces in such a position that the action of 
the wind upon it would counterbalance 
the effect of the travel of the center of 
pressure on the main surfaces. Thus 
changes in the direction and velocity of 
the wind would have little disturbing ef- 
fect, and the operator would be required 
to attend only to the steering of the ma- 
chine, which was to be effected by curv- 
ing the foi'ward surface up or down. 
The lateral equilibrium and the steering 
to right or left was to be attained by a 
peculiar torsion of the main surfaces, 
which was equivalent to presenting one 



» 



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end of the wings at a greater angle than 
the other. In the main frame a few 
changes were also made in the details of 
construction and trussing employed by 
Mr. Chanute. The most important of 
these were: ( 1 ) The moving of the for- 
ward main cross-piece of the frame to 
the extreme front edge; (2) the encasing 
in the cloth of all cross-pieces and ribs of 
the surfaces; (3) a rearrangement of the 
wires used in trussing the two surfaces 
together, which rendered it possible to 
tighten all the wires by simply shortening 
two of them. 

With these plans we proceeded in the 
summer of 1900 to Kitty Hawk, North 
Carolina, a little settlement located on 
the strip of land that separates Albemarle 
Sound from the Atlantic Ocean. Owing 
to the impossibility of obtaining suitable 
material for a 200-square-foot machine, 
we were compelled to make it only 165 
square feet in area, which, according to 
the Lilienthal tables, would be supported 
at an angle of three degrees in a wind of 
about 21 miles per hour. On the very 
day that the machine was completed the 
wind blew from 25 to 30 miles per hour, 
and we took it out for a trial as a kite. 
We found that while it was supported 
with a man on it in a wind of about 25 
miles, its angle was much nearer 20 de- 
grees than three degrees. Even in gusts 
of 30 miles the angle of incidence did not 
get as low as three degiees, although the 
wind at this speed has more than twice 
the lifting power of a 21-mile wind. As 
winds of 30 miles per hour are not plen- 




tiful on clear days, it was at once evident 
that our plan of practicing by the hour, 
day after day, would have to be post- 
poned. Our system of twisting the sur- 
faces to regulate the lateral balance was 
tried and found to be much more effec- 
tive than shifting the operator's body. 
On subsequent days, when the wind was 
too light to support the machine with a 
man on it, we tested it as a kite, working 
the rudders by cords reaching to the 
ground. The results were very satisfac- 
tory, yet we were well aware that this 
method of testing is never wholly con- 
vincing until the results are confirmed by 
actual gliding experience. 

We then turned our attention to mak- 
ing a series of actual measurements of 
the lift and drift of the machine under 
various loads. So far as we were aware, 
this had never previously been done with 
any full-size machine. The results ob- 
tained were most astonishing, for it ap- 
peared that the total horizontal pull of 
the machine, wliile sustaining a weight 
of 52 lbs., was only 8.5 lbs., which was 
less than had previously been estimated 
for head resistance of the framing alone. 
Making allowance for the weight carried, 
it appeared that the head resistance of 
the framing was but little more than 50 
per cent, of the amount which Mr. 
Chanute had estimated as the head re- 
sistance of the framing of his machine. 
On the other hand, it appeared sadly de- 
ficient in lifting power as compared with 
the calculated lift of curved surfaces of 
its size. This deficiency we supposed 
might be due to one or more of the fol- 
lowing causes: — (1) That the depth of 
the curvature of our surfaces was insuf- 
ficient, being only about one in 22, in- 
stead of one in 12. (2) That the cloth 
used in our wings was not sufficiently air- 
tight. (3) That the Lilienthal tables 
might themselves be somewhat in error. 
We decided to arrange our machine for 



u 



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the following year so that the depth of 
the curvature of its surfaces could be 
varied at will and its covering air- 
proofed. 

Our attention was next turned to glid- 
ing, but no hill suitable for the purpose 
could be found near our camp at Kitty 
Hawk. This compelled us to take the ma- 
chine to a point four miles south, where 
the Kill Devil sand hill rises from the flat 
sand to a height of more than 100 feet. 
Its main slope is toward the northeast, 
and has an inclination of 10 degrees. On 
the day of our arrival the wind blew 
about 25 miles an hour, and as we had 
had no experience at all in gliding, we 
deemed it unsafe to attempt to leave the 
ground. But on the day following, the 
wind having subsided to 14 miles per 
hour, we made about a dozen glides. It 
had been the original intention that the 
operator should run with the machine to 
obtain initial velocity, and assume the 
horizontal position only after the ma- 
chine was in free flight. When it came 
time to land he was to resume the up- 
right position and alight on his feet, 
after the style of previous gliding ex- 
periments. But in actual trial we found 
it much better to employ the help of two 
assistants in starting, which the peculiar 
form of our machine enabled us readily 
to do; and in landing we found that it was 
entirely practicable to land while still re- 
clining in a horizontal position upon the 
machine. Although the landings were 
made while moving at speeds of more 
than 20 miles an hour, neither machine 
nor operator suffered any injury. The 
slope of the hiU was 9.5 deg., or a drop 
of one foot in six. We found that after 
attaining a speed of about 25 to 30 miles 
with reference to the wind, or 10 to 15 
miles over the ground, the machine not 
only glided parallel to the slope of the 
hill, but greatly increased its speed, thus 
indicating its ability to glide on a some- 



what less angle than 9.5 deg., when we 
should feel it safe to rise higher from the 
surface. The control of the machine 
proved even better than we had dared to 
expect, responding quickly to the slight- 
est motion of the rudder. With these 
glides our experiments for the year 1900 
closed. Although the hours and hours 
of practice we had hoped to obtain finally 
dwindled down to about two minutes, 
we were very much pleased with the gen- 
eral results of the trip, for, setting out as 
we did with almost revolutionary the- 
ories on many points and an entirely un- 
tried form of machine, we considered it 
quite a point to be able to return without 
having our pet theories completely 
knocked on the head by the hard logic 
of experience, and our own brains 
dashed out in the bargain. Everything 
seemed to us to confirm the correctness 
of our original opinions — (1) that prac- 
tice is the key to the secret of flying; (2) 
that it is practicable to assume the hori- 
zontal position; (3) that a smaller sur- 
face set at a negative angle in front of 
the main bearing surfaces, or wings, will 
largely counteract the effect of the fore 
and aft travel of the center of pressure; 
(4) that steering up and down can be at- 
tained with a rudder without moving the 
position of the operator's body; (5) that 
twisting the wings so as to present their 
ends to the wind at different angles is a 
more prompt and efficient way of main- 
taining lateral equilibrium than that em- 
ployed in shifting the body of the oper- 
ator of the machine. 

When the time came to design our new 
machine for 1901 we decided to make it 
exactly like the previous machine in the- 
ory and method of operation. But as the 
former machine was not able to support 
the weight of the operator when flown 
as a kite, except in very high winds and 
at very large angles of incidence, we de- 
cided to increase its lifting power. Ac- 



is 



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corcjingly, the curvature of the surfaces 
was increased to one in 12, to confonn to 
the shape on which LiUenthal's table was 
based, and to be on the safe side we de- 
cided also to increase the area of the ma- 
chine from 165 square feet to 308 square 
feet, although so large a machine had 
never before been deemed controllable. 
The Lilienthal machine had an area of 
151 square feet; that of Pilcher, 165 
square feet; and the Chanute double- 
decker, 134 square feet. As our system 
of control consisted in a manipulation of 
the surfaces themselves instead of shift- 
ing the operator's body, we hoped that 
the new machine would be controllable, 
notwithstanding its great size. Accord- 
ing to calculations, it would obtain sup- 
port in a wind of 17 miles per hour with 
an angle of incidence of only three de- 
grees. 

Our experience of the previous year 
having shown the necessity of a suitable 
building for housing the machine, we 
erected a cheap frame building, 16 feet 
wide, 25 feet long, and 7 feet high at the 
eaves. As our machine was 22 feet wide, 
14 feet long (including the rudder), and 
about 6 feet high, it was not necessary to 
take the machine apart in any way in or- 
der to house it. Both ends of the build- 
ing, except the gable parts, were made 
into doors which hinged above, so that 
when opened they formed an awning at 
each end and left an entrance the full 
width of the building. We went into 
camp about the middle of July, and were 
soon joined by Mr. E. C. Huftaker, of 
Tennessee, an experienced aeronautical 




investigator in the employ of Mr. Cha- 
nute, by whom his services were kindly 
loaned, and by Dr. A. G. Spratt, of Penn- 
sylvania, a young man who has made 
some valuable investigations of the 
properties of variously curved surfaces 
and the travel of the center of pressure 
thereon. Early in August Mr. Chanute 
came down from Chicago to witness our 
experiments, and spent a week in camp 
with us. These gentlemen, with my 
brother and myself, formed our camping 
party, but in addition we had in many 
of our experiments the valuable assist- 
ance of Mr. W. J. Tate and Mr. Dan Tate, 

of Kitty Hawk. 

****** 

It had been our intention when build- 
ing the machine to do most of the 
experimenting in the following manner: 
— When the wind blew 17 miles an hour, 
or more, we would attach a rope to the 
machine and let it rise as a kite with the 
operator upon it. When it should reach 
a proper height the operator would cast 
off the rope and glide down to the ground 
just as from the top of a hill. In this way 
we would be saved the trouble of carry- 
ing the machine uphill after each glide, 
and could make at least 10 glides in the 
time required for one in the other way. 
But when we came to try it we found that 
a wind of 17 miles, as measured by Rich- 
ards' anemometer, instead of sustaining 
the machine with its operator, a total 
weight of 240 lbs., at an angle of inci- 
dence of three degrees, in reality would 
not sustain the machine alone — 100 lbs. 
— at this angle. Its lifting capacity 
seemed scarcely one-third of the calcu- 
lated amount. In order to make sure that 
this was not due to the porosity of the 
cloth, we constructed two small experi- 
mental surfaces of equal size, one of 
which was aii'-proofed and the other left 
in its natural state; but we could detect 
no difference in their lifting powers. 



80 



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AIRPLANE 



For a time we were led to suspect that the 
lift of curved surfaces little exceeded 
that of planes of the same size, but fur- 
ther investigation and experiment led to 
the opinion that (1) the anemometer 
used by us over-recorded the true ve- 
locity of the wind by nearly 15 per cent.; 
12) that the well-known Smeaton coefJi- 
[ent of .005 V ^ for the wind pressure at 
degrees is probably too great by at 
least 20 per cent.; (3) that Lilienthal's es- 
timate that the pressure on a curved sur- 
face having an angle of incidence of 
three degrees equals .545 of the pressure 
at 90 degrees is too large, being narly 50 
per cent, greater than very recent experi- 
ments of our own with a special pressure 
testing machine indicate; (4) that the su- 
perposition of the surfaces somewhat re- 
duced the lift per square foot, as com- 
pared with a single surface of equal area. 
In gliding experiments, however, the 
amount of lift is of less relative import- 
ance than the ratio of lift to drift, as this 
alone decides the angle of gliding de- 
scent. In a plane the pressure is always 
perpendicular to the surface, and the 
ratio of lift to drift is therefore the same 
as that of the cosine to the sine of the 
angle of incidence. But in curved sur- 
faces a verj^ remarkable situation is 
found. The pressure, ijistead of being 
uniformly normal to the chord of the arc, 
is usually inclined considerably in front 
of the perpendicular. The result is that 
the lift is greater and the drift less than 
if the pressure were normal. Lilienthal 
was the first to discover this exceedingly 
though our measurements differ consid- 
erably from those of Lilienthal. While 
important fact, which is fully set forth 
in his book, "Bird Flight the Basis of the 
Flying Art," but owing to some errors in 
the methods he used in making measure- 
ments, question was raised by other in- 
vestigators not onlj' as to the accuracy of 
Ais figures, but even as to the existence of 



any tangential force at all. Our experi- 
ments confirm the existence of this force, 
at Kitty Hawk we spent much time in 
measuring the horizontal pressure on 
our unloaded machine at various angles 
of incidence. We found that at 13 de- 
grees the horizontal pressure was about 
23 lbs. This included not only the drift 
proper, or horizontal component of the 
pressure on the side of the surface, but 
also the head resistance of the framing 
as well. The weight of the machine at 
the time of this test was about 108 lbs. 
Now, if the pressure had been normal to 
the chord of the surface, the drift proper 
would have been to the lift (108 lbs.) as 
the sine of 13 degrees is to the cosine of 

13 degrees, or^?^^^ = 24 + lbs.; but 

this slightly exceeds the total pull of 23 
lbs. on our scales. Therefore, it is evi- 
dent that the average pressure on the sur- 
face, instead of being normal to the 
chord, was so far inclined toward the 
front that all the head resistance of fram- 
ing and wires used in the construction 
was more than overcome. In a wind of 

14 miles per hour resistance is by no 
means a negligible factor, so that tang- 
ential is evidently a force of considerable 
value. In a higher wind, which sustained 
the machine at an angle of 10 degrees, the 
pull on the scales was 18 lbs. With the 
pressure normal to the chord the drift 



proper would have been 



.17 X 98 
.98 



17 



lbs., so that, although the higher wind ve- 
locity must have caused an increase in 




THE 



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the head resistance, the tangential force 
still came within one pound of overcom- 
ing it. After our return from Kitty 
Hawk we began a series of experiments 
to accurately detennine the amount and 
direction of the pressure produced on 
curved surfaces when acted upon by 
winds at the various angles from zero to 
90 degrees. These experhnents are not 
yet concluded, but in general they sup- 
port Lilienthal in the claim that the 
curves give pressures more favorable in 
amount and direction than planes; but 
we find marked differences in the exact 
values, especially at angles below 10 de- 
grees. We were unable to obtain direct 
measurements of the horizontal pres- 
sures of the machine with the operator 
on board, but by comparing the distance 
traveled in gliding with the vertical fall, 
it was easily calculated that at a speed of 
24 miles per hour the total horizontal re- 
sistance of our machine when bearing 
the operator, amounted to 40 lbs., which 
is equivalent to about 2 1/3 horse-power. 
It must not be supposed, however, that a 
motor developing this power would be 
sufficient to drive a man-bearing ma- 
chine. The extra weight of the motor 
would require either a larger machine, 
higher speed, or a greater angle of inci- 
dence in order to support it, and there- 
fore more power. It is probable, how- 
ever, that an engine of six horse-power, 
weighing 100 lbs., would answer the pur- 
pose. Such an engine is entirely practi- 
cable. Indeed, working motors of one- 
half this weight per horse-power (9 lbs. 
per horse-power) have been constructed 
by several different builders. Increasing 
the speed of our machine from 24 to 33 




miles per hour reduced the total horizon- 
tal pressure from 40 to about 35 lbs. This 
was quite an advantage in gliding, as it 
made it possible to sail about 15 per cent, 
further with a given drop. However, it 
would be of little or no advantage in re- 
ducing the size of the motor in a power- 
driven machine, because the lessened 
thrust would be counter-balanced by the 
increased speed per minute. Some years 
ago Professor Langley called attention to 
the great economy of tlirust which might 
be obtained by using very high speeds, 
and from this many were led to suppose 
that high speed was essential to success 
in a motor-driven machine. But the 
economy to which Professor Langley 
called attention was in foot-pounds per 
mile of travel, not in foot pounds per 
minute. It is the foot-pounds per min- 
ute that fixes the size of the motor. The 
probability is that the first flying ma- 
chines will have a relatively low speed, 
perhaps not much exceeding 20 miles per 
hour, but the problem of increasing the 
speed will be much simpler in some re- 
spects than that of increasing the speed 
of a steamboat; for, whereas in the latter 
case the size of the engine must increase 
as the cube of the speed, in the flying ma- 
chine, until extremely high speeds are 
reached, the capacity of the motor in- 
creases in less than simple ratio; and 
there is even a decrease in the fuel con- 
sumption per mile of travel. In other 
words, to double the speed of a steam- 
ship (and the same is true of the balloon 
type of airship) eight times the engine 
and boiler capacity would be required, 
and four times the fuel consumption per 
mile of travel; while a flying machine 
would require engines of less than 
double the size, and there would be an 
actual decrease in the fuel consumption 
per mile of travel. But looking at the 
matter conversely, the great disadvan- 
tage of the flying machine is apparent; 



8S 



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for in the latter no flight at all is possible 
unless the proportion of horse-power to 
flying capacity is very high; but on the 
other hand a steamship is a mechanical 
uccess if its ratio of horse-power to ton- 
nage is insignificant. A flying machine 
that would fly at a speed of 50 miles an 
hour with engines of 1 ,000 horsepower 
would not be upheld by its wings at all at 
a speed of less than 25 miles an hour, and 
nothing less than 500 horse-power could 
drive it at this speed. But a boat which 
could make 40 miles per hour with en- 
gines of 1,000 horse-power would still 
move four miles an hour even if the en- 
gines were reduced to one horse-power. 
The problems of land and water travel 
were solved in the nineteenth century, 
because it was possible to begin with 
small achievements and gradually work 
up to our present success. The flying 
prolem was left over to the twentieth 
century, because in this case the art must 
be highly developed before any flight of 
any considerable duration at aU can be 
obtained. 

However, there is another way of fly- 
ing which requires no artificial motor, 
and many workers believe that success 
will first come by this road. I refer to 
the soaring flight, by which the machine 
is permanently sustained in the air by 
the same means that are employed by 
soaring birds. They spread their wings 
to the wind, and sail by the hour, with no 
perceptible exertion beyond that re- 
quired to balance and steer themselves. 
What sustains them is not definitely 
known, though it is almost certain that it 
is a rising current of air. But whether 
it be a rising current or something else, 
it is as well able to support a flying ma- 
chine as a bird, if man once learns the art 
of utilizing it. In gliding experiments it 
has long been known that the rate of ver- 
tical descent is very much retarded, and 
the duration of the flight greatly pro- 



longed, if a strong wind blows up the face 
of the hill parallel to its surface. Our 
machine, when gliding in still air, has a 
rate of vertical descent of nearly six feet 
per second, while in a wind blowing 26 
miles per hour up a steep hill we made 
glides in which the rate of descent was 
less than two feet per second. And dur- 
ing the larger part of this time, while the 
machine remained exactly in the rising 
current, there was no descent at all, but 
even a slight rise. If the operator had 
had sufficient skill to keep himself from 
passing beyond the rising current he 
would have been sustained indefinitely 
at a higher point than that from which 

he started. 

****** 

In looking over our experiments of 
the past two years, with models and full- 
size machines, the following points stand 
out with clearness: — 

1. That the lifting power of a large 
machine, held stationary in a wind at a 
small distance from the earth, is much 
less than the Lilienthal table and our own 
laboratory experiments would lead us to 
expect. When the machine is moved 
through the air, as in gliding, the discrep- 
ancy seems much less marked. 

2. That the ratio of drift to lift in 
well-balanced surfaces is less at angles 
of incidence of five degrees to 12 de- 
grees than at an angle of three degrees. 

3. That in arched surfaces the center 
of pressure at 90 degrees is near the cen- 
ter of the surface, but moves slowly f or- 








23 



THE 



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HISTORY 



O F 



THE 



AIRPLANE 



ward as the angle becomes less, till a 
critical angle varying with the shape and 
depth of the curve is reached, after which 
it moves rapidly toward the rear till the 
angle of no lift is found. 

4. That with similar conditions large 
surfaces may be controlled with not 
much greater difficulty than small ones, 
if the control is effected by manipulation 
of the surfaces themselves, rather than 
by a movement of the body of the oper- 
ator. 

5. That the head resistances of the 
framing can be brought to a point much 



below that usually estimated as neces- 
sary. 

6. That tails, both vertical and hori- 
zontal, may with safety be eliminated in 
gliding and other flying experiments. 

7. That a horizontal position of the 
operator's body may be assumed without 
excessive danger, and thus the head re- 
sistance reduced to about one-fifth that 
of the upright position. 

8. That a pair of superposed, or tan- 
dem, surfaces has less lift in proportion 
to drift than either surface separately, 
even after making allowance for weight 
and head resistance of the connections. 




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